Enhanced between/3

2020-05-13 21:19:47 +02:00
parent 6d6f6ed8fc
commit a86019d53b
1 changed files with 5 additions and 1 deletions
--- a/src/prolog/lib/between.pl
+++ b/src/prolog/lib/between.pl
@@ -9,7 +9,11 @@ between(Lower, Upper, X) :-
    must_be(integer, Lower),
    must_be(integer, Upper),
    can_be(integer, X),
-    between_(Lower, Upper, X).
+    (   nonvar(X) ->
+        Lower =< X,
+        X =< Upper
+    ;   between_(Lower, Upper, X)
+    ).

 between_(Lower, Upper, Lower) :-
    Lower =< Upper.